Honeymoon With U.S. Over, Russian Says : Diplomacy: But no divorce looms, Kozyrev declares after talks with Christopher on differences over Iran and Chechnya.

Russian Foreign Minister Andrei V. Kozyrev said Thursday that the Washington-Moscow “honeymoon has come to an end” as he and Secretary of State Warren Christopher failed to resolve major differences that have emerged in the relationship between the former Cold War enemies.

The two diplomats did manage to paper over a festering dispute about Russia’s planned $1-billion sale of nuclear technology to Iran by turning the matter over to a new U.S.-Russia study group, which was told to prepare a report before President Clinton and Russian President Boris N. Yeltsin meet in Moscow in May.

But in a joint news conference, the foreign ministers bickered openly over the Iran deal’s implications. Christopher said he told Kozyrev “of our strong opposition to Russian nuclear cooperation with Iran” and indicated he had handed him secret intelligence to support the point.

Kozyrev insisted, however, that “we don’t see any problem here” because the Iranian deal will be subjected to international safeguards.

They also demonstrated a sharp disagreement over future Russian participation in the annual summit of the world’s leading economic powers. Kozyrev said Russia wants “a broader degree of participation” for Yeltsin in June at the planned Halifax, Canada, summit of the Group of Seven nations. But Christopher said there will be no upgrade in Russian participation as long as fighting continues in Chechnya.

Both agreed that the main purpose of their two-day meeting was to set the agenda for the Clinton-Yeltsin summit that will follow celebrations on May 9 in Moscow of the 50th anniversary of the end of World War II in Europe. They said they will meet again next month.

But it was clear that the good feeling that followed the end of the Cold War is long over. Picking up a metaphor used in a question from a Russian journalist, Kozyrev said: “Indeed, the honeymoon has come to an end.” But he said there will be no divorce and “something that we won’t allow to happen is unfaithfulness.” He said that the countries now have developed “an ability to resolve jointly the problems that we face.”

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For his part, Christopher acknowledged friction in the relationship but said, “Where there are differences, we are determined to address them forthrightly, fully and candidly.”

In a joint statement, they announced the creation of a committee of experts from both countries to “review regional and global developments that pose a threat to our common efforts to halt the spread of weapons of mass destruction.”

Despite disagreement over what Russia maintains is the sale of peaceful nuclear technology to Iran--a country the United States calls “a rogue state”--Washington and Moscow support indefinite extension of the 25-year-old Nuclear Non-Proliferation Treaty, which expires this year.

Russia has agreed to a contract, initially worth about $800 million to $1 billion, to help Iran build a nuclear plant at Bushehr on the Persian Gulf.

In the joint news conference, Kozyrev said Russia has advanced “some new ideas” to end the war in Bosnia-Herzegovina. But he did not spell them out and insisted Russia will do nothing to break the unity of the five-nation Contact Group, which has failed so far to come up with a plan that all sides will accept.

“We tried to find ways of nudging the parties toward a constructive conclusion,” he said. “You can call it a . . . set of new ideas coming from us for discussion.”

U.S. officials said Kozyrev made no new proposals in his private meetings with Christopher, except to suggest that the Contact Group--the United States, Russia, Britain, France and Germany--should seek small steps that might lead to a settlement instead of trying to put together a comprehensive package.

Christopher underlined continuing U.S. objections to Russia’s military offensive in Chechnya. But Kozyrev avoided a public confrontation over the issue by ignoring it in his public comments.

Meantime, in Chechnya, Russian troops overran and captured the rebel stronghold of Argun, Gen. Anatoly Kulikov informed Moscow from the mobile military information center. His dispatch said that Argun was taken “without damaging the town,” but independent reports acknowledged that there had been casualties on both sides.

Russian forces stepped up their 3 1/2-month-old offensive Monday--the same day Clinton agreed to take part in the Moscow World War II events, despite widespread concerns that his visit with Yeltsin would undermine U.S. denunciations of the deadly intervention in Chechnya.

Times staff writer Carol J. Williams in Moscow contributed to this report.